Newsletter of Penn Dutch Cow Care                                                        July 2002

Hi Folks,        

            Is it hot enough for you?!   J

            The summer heat is already here! First I’d like to say that Penn State’s latest “Dairy Focus” newsletter gives excellent information on what heat and humidity do to dairy cows as far as feed intake, milk production, and reproduction. Since you might not yet have read it, I’ll highlight it. (If you have read it, it is worth repeating.)

Briefly, humidity combined with heat is what really drags down cows. Temperatures above 90 degrees with low humidity are when cows become uncomfortable, but temperatures as low as 75-80 degrees with high humidity will already have cows drop feed intake by a third and an associated drop in milk occurs. High producers, just-fresh and near-fresh animals will suffer the most. When we experience hazy, hot, humid weather, cows’ nutrient requirements can increase some 15-20% due to their panting, sweating, and urinating. Sweating depletes potassium and urinating depletes sodium, in addition to water loss. Your cows may not be as interested in eating when they are panting, but they probably will be interested in drinking clean and fresh water. Do not make your cows walk far or search for water!! Besides being the most important nutrient in their regular diet, it is essential to prevent dehydration and keep them cool. The moisture in grazed paddocks is not enough for their needs. Supply water.

Some other things to keep in mind are shade and ventilation. However, one shade tree is worse than no trees. A mucky area under one or a couple trees will create more health problems than no shade at all. (But, don’t go out and chop down your tree!) On the worst days, in tie-stall barns with good tunnel ventilation, it is more beneficial to keep the cows in during the day and let them out to graze or exercise at night.  

One major health issue I worry about as a vet during the heat is mastitis—especially mastitis in dry, near-fresh and fresh cows. The effects of humidity on a cow that leaks milk or has a dirty udder spells trouble. Usually dry cows are not watched as closely until they are mopey and observed not eating quite right. Usually, with a simple examination, they are found to have a fever and a hard quarter. They are a day or two (or longer) into  the sickness at this point. A critical problem is that the calf may be aborted, either due to the toxins created by the mastitis germs and/or due to the fever itself. Fever reduction and re-hydration are mandatory—this usually requires IV fluids for re-hydration, and anti-pyretics such as aspirin, flunixin (Banamine), or aconite and belladonna (natural plant derivatives). Whether or not one wants to use an antibiotic is a choice that should be made on a case-by-case basis.

Typically, dry cows tend to get coliform or corynebacteria (arcanobacter) mastitis. When the animal is finally tended to, the quarter itself will usually be irreversibly damaged and rock-hard. If it is coryne mastitis (symptoms of thick chunks and a slightly green-tinged yellow pus that really stinks), using good ol’ penicillin can save the cow. Whether or not the calf survives to term, is born dead, or is aborted cannot be predicted accurately. If the cow aborts, has no udder to speak of, and has penicillin loaded in her, that will make her a beef cow later. But not treating a coryne mastitis can lead to gas  gangrene mastitis and a more immediate loss of the animal.

If it is a coliform mastitis (watery, “lemonade-like” secretions) in a dry cow, the same set of problems come up regarding the calf. But the antibiotic choice would not include penicillin. It would include oxytetracycline (LA-200) or ampicillin (both have withholding times), or ceftiofur (Naxcel, no withholdings) to allow flexibility to ship the animal quickly if needed.

In fresh cows that leak milk, the heat and humidity along with wood shavings in the bedding or a mucky area under a shade tree make for problems. If you have mattresses, do not use any shavings until the humidity lessens. Simply use lime or straw/ fodder under the cows back feet upon the mattresses. Straw is fairly inert, if replaced regularly. Sand is totally inert but doesn’t work well with gravity flow manure pits. (Using straw/ fodder will also decrease moisture in the gutter, which will help also reduce fly-growing areas.)

Fresh cows need to be treated the same way as dry cows for dehydration and fever. Udder Mint, a peppermint ointment, is a very soothing and cooling product that cows seem to like when they have a hot mastitis. Stripping out all the initial secretions is also important. Using B-vitamins and probiotics to help the appetite and rumen is important, as is vitamin C as an antioxidant, especially if the rumen is shut down and not creating its own vitamin C.

One area probably under-utilized by many farmers is vaccinating with “J-5” or “Endovac-Bovi” to prevent the terrible effects of coliform mastitis. An animal may still get a watery quarter but there will only be a minimal fever (if any), the udder won’t be rock-hard (only mildly swollen), she will still eat some, and the treatment costs will be minimized with the treatment outcome much improved. I highly recommend vaccinating against coliform. This also helps prevent calf scours. Just don’t vaccinate (with anything) on a hot day! Wait for a cooler day. Remember, a cow’s body temperature peaks about 3-4 hours after the peak temperature of the day. It is still in time right now to begin vaccinating your dry-off cows before the next surge in hot, hazy and humid weather. You can further help your dry cows during this heat by boosting their immune system at dry-off and 2 weeks before freshening with a shot of Vitamin E and Selenium (MuSe).